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ARRL Propagation Bulletin ARLP010 (2016)

ARLP010 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 10  ARLP010
From Tad Cook, K7RA
Seattle, WA  March 4, 2016
To all radio amateurs 

ARLP010 Propagation de K7RA

Average daily sunspot numbers over our reporting week (February 25
through March 2) were marginally higher than the previous seven
days, going from 37.9 to 41.4, while average daily solar flux was
down by just one point, to 92.9.
Average planetary A index changed from 10.1 to 5.9 and average
mid-latitude A index went from 12.6 to 5.3., so it was a quiet week
with stable geomagnetic conditions.
Predicted solar flux from USAF/NOAA for the near term is 100 on
March 4-7, 105 on March 8-13, 100 on March 14-15, 95 on March 16-20
and then bottoming out at 90 on March 21-26. Flux values then peak
at 115 on March 30-31.
The planetary A index prediction shows 12, 15, 20, 15 and 10 on
March 4-8, then 8 on March 9-11, 5 on March 12 and 12 on March 13.
The predicted A index then makes a huge jump to 30 on March 14-16.
This perhaps is from a recurring coronal hole, because on April
10-12 the A index again goes to 30. Note that in mid-February there
were similar numbers on February 17-19 of 38, 34 and 29.
Petr Kolman, OK1MGW of the Czech Propagation Interest Group
(actually they call it the Propagation Interested Group, but I
suspect Interest Group is a better translation to standard American
English) sent his outlook for geomagnetic conditions. He says to
expect quiet to unsettled conditions on March 4, quiet to active
March 5-6, quiet to unsettled March 7-8, quiet to active March 9-10,
quiet to unsettled March 11-12, quiet to active March 13, active to
disturbed March 14-16, quiet to active March 17, mostly quiet March
18-19, quiet on March 20-21, mostly quiet March 22-24, quiet March
25-26, quiet to unsettled March 27, quiet to active March 28-29, and
quiet to unsettled March 30.
Petr expects an increase in solar wind on March 5-6, 9-10, 13-16 and
Notice that his expected active to disturbed conditions on March
14-16 lines up with the prediction for an A index of 30 on those
same dates from USAF/NOAA.
February is done, so let's examine our 3-month moving average of
sunspot numbers.
According to our own data, cycle 24 peaked with a 3-month moving
average of 146.4 and 148.2 centered on February and March of 2014.
Four months later the moving average centered on July 2014 was
109.2, and December 2014 was 107.8. January 2015 was 98.2, the first
time the average was below 100 since September 2013. July 2015 was
69.1, December 2015 was 55.4, and the latest number centered on
January 2016 was 53.5. The moving average centered on January is an
arithmetic average of daily sunspot numbers from December 1, 2015
through February 29, 2016. Adding all sunspot numbers for those days
totals 4,868 and divided by 91 days yields an average of 53.4945 or
The last time the average was at this level was February 2011, five
years ago, when it was 55.7.
The ARRL International SSB DX Contest is this weekend, and it runs
from 0000 UTC March 5 through 2359 UTC March 6. See for details.
Eric Guzman, NP3A had a comment on N0JK's note about what a
difference a year makes on 10 meters. Eric wrote "I think is not
only 10 meters. This February I will complete one year of monthly
reports using our Club Skimmer KP3Z data.
Comparing the 2015 to 2016 tally for the ARRL DX CW Contest, 80
meter activity was down 9 percent, 40 was up 9 percent, 20 meters
down 20 percent, 15 meters down 75 percent and 10 meters down 89
percent. I believe this is just the number of call signs copied, but
it was 14,503 on 10 meters last year, and only 1,644 this year."
Eric notes, "Full SH5 reports for both weekends can be found here:
Huge difference on 15 meters as well. Of course there are other
factors that affect these numbers like participation, but in general
propagation is the main factor."
Thanks Eric. 40 meters was the only band with an increased count,
and with propagation down on 10, 15 and 20 meters, where else would
you go?
For more information concerning radio propagation, see the ARRL
Technical Information Service at For an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at More good
information and tutorials on propagation are at
My own archives of the NOAA/USAF daily 45 day forecast for solar
flux and planetary A index are in downloadable spreadsheet format at and .
Click on "Download this file" to download the archive, and ignore
the security warning about file format. Pop-up blockers may suppress
the download.
Monthly propagation charts between four USA regions and twelve
overseas locations are at
Instructions for starting or ending email distribution of ARRL
bulletins are at
Sunspot numbers for February 25 through March 2 were 26, 41, 37, 38,
44, 39, and 65, with a mean of 41.4. 10.7 cm flux was 91.7, 89,
90.4, 93.2, 90.9, 96.8, and 98.2, with a mean of 92.9.  Estimated
planetary A indices were 5, 7, 4, 4, 5, 9, and 7, with a mean of
5.9. Estimated mid- latitude A indices were 6, 5, 3, 4, 4, 8, and 7,
with a mean of 5.3.


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